Investigation of acid-base and sorption properties of surface of metal-ceramic composites

The acid-base properties of the surface of composites based on boron, silicon, and sialon nitrides were investigated by the indicator method of Hammett and Tanabe with spectrophotometric indication. Identification of the surface sites of the composites under study was carried out. On the surface of composites based on boron and sialon nitrides the Lewis base sites dominate, while on the surface of samples based on silicon nitride the Brønsted acid sites. Sorption of dyes and oxalic acid by cermet materials was studied. It is shown that the adsorption activity depends on the nature and amount of surface active sites of the composites

Bio-Templating: An Emerging Synthetic Technique for Catalysts. A Review

In the last few years, researchers have focused their attention on the synthesis of new catalyst structures based on or inspired by nature. Biotemplating involves the transfer of biological structures to inorganic materials through artificial mineralization processes. This approach offers the main advantage of allowing morphological control of the product, as a template with the desired morphology can be pre-determined, as long as it is found in nature. This way, natural evolution through millions of years can provide us with new synthetic pathways to develop some novel functional materials with advantageous properties, such as sophistication, miniaturization, hybridization, hierarchical organization, resistance, and adaptability to the required need. The field of application of these materials is very wide, covering nanomedicine, energy capture and storage, sensors, biocompatible materials, adsorbents, and catalysis. In the latter case, bio-inspired materials can be applied as catalysts requiring different types of active sites (i.e., redox, acidic, basic sites, or a combination of them) to a wide range of processes, including conventional thermal catalysis, photocatalysis, or electrocatalysis, among others. This review aims to cover current experimental studies in the field of biotemplating materials synthesis and their characterization, focusing on their application in heterogeneous catalysis

Possibility to use spent fluid catalytic cracking catalyst as component of Portland cement binders

Fluid cracking catalyst residue (spent FCC) is a by-product from petrol refineries. It primarily consists of zeolite (in used sample - faujasite) and amorphous aluminosilicates. In this study, possibility to use spent FCC as a component of binders with low content of Portland cement (PC) have been investigated. Binders made with high volume of mineral additions are being developed in order to reduce the amount CO2 emitted by PC industry. Fly ash (FA), a by-product of coal combustion in thermal power plants, is one of the most commonly used raw material for these binders. The main shortages of binders with high volume of FA are long setting time and low early strength. In this work, mixtures of PC, FA and spent FCC were prepared. It was found that addition of spent FCC to low PC mixtures significantly shortened setting time and improved early strength of the binders. However, 28-day compressive strength of the ternary binder was lower than the strength of low PC binder synthesized with FA only, which indicated the need for further optimization of the binder composition

Morphology-Controlled Synthesis of Nitrides from Titanium Dioxide and Titanium Disilicide by Ammonia Nitridation

芝浦工業大学2020年

Plasma-Enhanced Vapor Deposition Process for the Modification of Textile Materials

Nowadays many techniques are used for the surface modification of fabrics and textiles. Two fundamental techniques based on vacuum deposition are known as chemical vapor deposition (CVD) and physical vapor deposition (PVD). In this chapter, the effect of plasma-enhanced physical and chemical vapor deposition on textile surfaces is investigated and explained

Photocatalytic degradation of chloramphenicol using iron-containing metal-ceramic composites under visible-light conditions

Синтезированы железосодержащие металлокерамические композиты на основе нитрида кремния, модифицированного полупроводниковым соединением TaON, методом автоволнового горения в азоте ферросиликоалюминия с различными добавками (5, 10, 15 мас. %) металлического тантала. Методом рентгеновской дифракции установлен фазовый состав, методом сканирующей электронной микроскопии изучена морфология поверхности композитов. Проведена количественная оценка поверхностного железа с применением приставки к растровому электронному микроскопу для микрорентгеноспектрального анализа. Исследованы кислотно-основные свойства поверхности композитов мето-дом рН-метрии и индикаторным методом Гаммета–Танабе со спектрофотометрической индикацией. Проведена интегральная оценка кислотности поверхности композитов, идентифицированы поверхностные центры исследуемых композитов. Установлен широкий набор кислотно-основных центров (основных центров Льюиса, рКа –0,29), кислотных центров (рКа 1,3–6,5) и основных центров Брен-стеда (рКа 7–13), что указывает на адсорбционную активность композитов к различным поллютантам. Изучена адсорбция хлорамфеникола (CHL), предложены механизмы адсорбционных процессов. Установлена корреляция адсорбционной активности композитов к СHL (рКа1 = 5,5; рКа2 = 11,3) с их кислотными свой-ствами. Исследована фотокаталитическая активность композитов в процессе окислительной деструкции CHL. Железосодержащие металлокерамические композиты на основе нитрида кремния, модифицированного TaON, с добавкой Н2О2 являются перспективными фотокатализаторами для окислительной деструкции СHL (85–91%) в условиях облучения видимым светом. Высокая активность обусловлена адсорбционными свойствами композитов и совмещением гетероген-ного фотокатализа и гомогенной системы фото-Фентона

Nial and steel as matrices and tic and oxynitrides as reinforcements in metal-matrix composite fabrication

Philosophiae Doctor - PhDMetal matrix composites harness the superior attributes of their individual constituents to form high performance materials that would rather be impossible from monolithic substances. Owing to many possible combinations, a myriad of metal matrix composite systems can be fabricated with a metal (or a metal alloy) as a matrix (continuous) phase and a ceramic as a reinforcement (discontinuous) phase. The current study focuses on two matrices, namely Nickel Aluminide and Austenitic Steel as well as two reinforcements namely, Titanium Carbide and Oxynitrides. NiAl alloys are candidates for high temperature structural materials due to their high melting temperature, low density, good thermal conductivity, and excellent oxidation resistance

SYNTHESIS AND CHARACTERIZATION OF NICKEL ZINC FERRITES

In this study we have prepared nickel ferrite (NF) and nickel zinc ferrite (NZF) nanoparticles by auto-combustion method starting from nickel, zinc and iron nitrates. After the process of self-ignition, fine precursor powder was thermally treated at 1000 °C for 1 h, forming nickel zinc ferrite powders, with molar ratio of Zn 0, 0.3, 0.5, 0.7. XRD characterization showed the formation of well crystallized nickel ferrite and nickel zinc ferrite inverse spinel structure without presence of secondary phases. Ceramic materials were obtained by uniaxial pressing at 196 MPa and sintering at 1250 °C for 4 h in the tube furnace. SEM images at the free surface showed that substitution of Ni2+ ions with Zn2+ ions results in larger grains and lower porosity, confirmed by density measurements. Magnetization results showed ferromagnetic behavior of the NF and NZF materials. Magnetic measurements of ferrites were carried out and presented in Fig. 1. Saturation magnetization moment of NF was lower than for N0.7Z0.3F and N0.5Z0.5F, but slightly higher than for N0.3Z0.7F. With increasing the ratio of Zn to 0.3, magnetization increases, because the Fe3+ ions in the octahedral site interact with other Fe3+ ions. The fields at which saturation occur was almost the same for all materials